This invention relates to a method and apparatus for processing biological fluids, such as blood or suspended cells, and, more specifically, to a disposable centrifuge apparatus in which biological fluids may be separated by being centrifuged. The centrifugal force separates the lighter density biological components from the heavier density biological components. For example, red blood cells, which are heavier, may be separated from plasma or platelet components which are lighter in density.
Since at least the early 1960's, a method and apparatus for the collection, separation and storage of a specific biological fluid, i.e., human blood or its components to use for transfusions and other purposes has been available. A key element in the development of apparatus for the separation of human blood into its component elements, has been the socalled "Latham Bowl". A typical Latham Bowl comprises a rotor in the form of a bowl body which is mounted on a chuck and which is adapted to rotate about a longitudinal axis extending through the bowl.
A core member may be provided within the bowl body to provide a zone between the bowl body and the core, within which the blood is separated into constituent components by the centrifugal forces acting on the blood. Whole blood is introduced into the bowl via a fixed, or stationary, feed tube mounted on a header. The feed tube extends into the bowl and is coaxial with the longitudinal axis of the bowl body.
An outlet, or effluent port, is formed coaxially about the inlet port to allow separated blood components to flow out of the centrifuge bowl. The inlet and outlet ports are connected to fixed members. For example, the inlet port may be connected through sterile tubing to a phlebotomy needle, which may be inserted into a donor for collection of blood. The outlet port may be connected, through sterile tubing, to a sterilized plasma collection container. Because of these connections, both of these ports must remain stationary and cannot be rotated along with the centrifuge bowl.
Accordingly, since their inception, Latham Bowl-type blood centrifuge processors have required some form of rotating seal between the stationary inlet and outlet ports and the rotating centrifuge bowl. (See, for example, U.S. Pat. No. 3,145,713 to A. Latham, Jr. issued Aug. 25, 1964; U.S. Pat. No. 3,317,127, issued May 2, 1967 to R.F. Cole; U.S. Pat. No. 3,409,213 issued Nov. 5, 1968 to A. Latham, Jr.; U.S. Pat. No. 3,565,330 issued Feb. 23, 1971 to A. Latham, Jr.; U.S. Pat. No. 3,581,981 issued June 1, 1971 to A. Latham, Jr.; U.S. Pat. No. 3,706,412 issued Dec. 19, 1972 to A. Latham, Jr.; U.S. Pat. No. 3,785,549 issued Jan. 15, 1974 to A. Latham, Jr.; and U.S. Pat. No. 4,300,717 issued Nov. 17, 1981 to A. Latham, Jr.)
The problem of coupling the fixed ports to the interior of the centrifuge bowl via a rotary seal has been of concern to those skilled in the art over the years. The prior art is replete with the efforts of those skilled in the art to improve the sealing capability of such rotary seals by improving the sealing function and the apparatus for supporting the header in a fixed axial position. The early seals, as embodied in U.S. Pat. No. 3,565,330, employed a rigid, low-friction member, which contacted a moving rigid member with minimal friction, forming a dynamic seal with a secondary elastomeric member which provided a resilient static seal and a spring action force between the surfaces of the dynamic seal.
Another rotary seal suitable for use in blood processing centrifuges is described in U.S. Pat. No. 3,801,142 issued to Jones et al. In this seal, a pair of seal elements, having confronting annular fluid-tight sealing surfaces of non-corrodable material, are provided These are maintained in a rotatable but fluid-tight relationship by axial compression of a length of elastic tubing forming one of the fluid connections to the seal elements. The Belco Company of Mirandola, Italy, developed a rotary seal which is employed in a blood processing centrifuge known as the "BT Bowl". In this seal, a ceramic ring member is attached to rotatable elements of the centrifuge and a fixed graphite ring is attached to stationary centrifuge elements. These ring members are in sealing relationship with each other. Additionally, an elastomeric diaphragm is attached at one end to an adapter ring for the graphite ring and, at the other end, to a stationary part of the centrifuge.
In the rotary centrifuge seal of U.S. Pat. No. 4,300,717, an improved rotary seal is described, which has a rotatable ring member and a non-rotatable ring member with sealing surfaces in sealing engagement with each other and wherein means are provided to entrap solid particulate matter on the side of the seal toward the blood pathway which may be generated at areas of contact between the two ring members during operation of the centrifuge. Further, means are provided for directing entrapped particles back to the area of contact between the ring members, so that the particles are ingested and expelled to the outside.
Despite all these efforts directed towards improving the rotary seal in Latham-type centrifuge bowls, the complexity of the rotary seal still remains a fundamental problem. By their very nature, such seals are difficult to design, manufacture and test. Furthermore, the Federal Drug Administration has not as yet approved blood components processed in such rotary seal-type bowls for use beyond twenty-four hours and, therefore such components cannot now be stored for extended time periods in the United States.
In an effort to overcome the problems associated with rotary seal centrifuge bowls, those skilled in the art have devised complicated systems, such as the so-called "skip rope technique", which enables blood to be coupled in and out of centrifuge containers for processing without requiring the rotary seal found in the prior art Latham bowl devices.
The "skip-rope" seal-less centrifuge is shown in FIG. 2 of U.S. Pat. 4,146,172 to Cullis et al. Basically, this apparatus comprises a rotor drive assembly to which a rotor assembly is journaled by means of a hollow support shaft. The rotor drive assembly is itself journaled to a stationary hub assembly by means of a vertical drive shaft.
A red blood cell separation chamber and a platelet collection chamber are seated on the rotor assembly. Fluid communication is established between the two chambers, which rotate with the rotor assembly, and the non-rotating portions of the processing system, by means of an umbilical cable which extends from a central location along the axis of rotation of the rotor downwardly through the center of the drive shaft, radially outwardly through a guide sleeve, and upwardly to a fixed axially aligned position established by a support arm. The routing of the umbilical cable, together with the rotor assembly and rotor drive assembly are driven in the same direction with a speed ratio of 2:1, to establish fluid communication between the two chambers without the cable becoming twisted. Variations of this "skip-rope" technique are shown in U.S. Pat. Nos. 4,425,112, 4,419,089 and 3,775,309.
The "skip-rope" technique carries its own associated drawbacks. The system is hard to load, requires a large diameter machine for orbiting an arm at half the rotation speed. Such large diameter machines are bulky and awkward, considering the intended use environment, i.e., hospitals. Such machines use a complicated medium gear mechanism and results in wear of the "skip-rope" tubing.
Accordingly, a need exists for a simple centrifuge apparatus and method whereby whole blood may be separated into its constituent components by centrifugal forces without use of rotary seals or complicated "skip-rope" mechanisms.